Trapezoidal back bias and trilayer reader geometry with predetermined magnetization shape
A magnetoresistive sensor is generally disclosed. Various embodiments of a sensor can have at least a trilayer sensor stack biased with a back biasing magnet adjacent a back of the trilayer sensor. The back biasing magnet, the trilayer sensor stack, or both have substantially trapezoidal shapes to enhance the biasing field and to minimize noise.
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This application is a divisional application of copending U.S. patent application Ser. No. 12/502,104 filed on Jul. 13, 2009.
SUMMARYA magnetoresistive sensor includes at least a trilayer sensor stack with a front width proximate an ABS, and a back width distal from an ABS and a back biasing magnet with a trapezoidal shape with a front width and a back width. The trapezoidal shape concentrates the magnetic field at the front of the biasing magnet in the vicinity of the sensor stack.
The various embodiments of shapes disclosed herein increase the performance of a reader by increasing the bias field at the front of a back bias magnet and by decreasing signal noise. The origin of these effects is shown in
By changing the geometry of a magnetic element, one or the other of the “C” and “S” states can be energetically favored.
The ABS view of trilayer read head 10 in
If spacer layer 26 is nonmagnetic, and electrically conducting, it may be fabricated from, for example, copper. If spacer layer 26 is nonconducting, it may be fabricated from, for example, aluminum oxide (Al2O3 or AlxO where x may or may not be an integer) or magnesium oxide. Ferromagnetic layers 22 and 24 may be fabricated from magnetic material such as, for example, nickel-iron-cobalt (Ni—Fe—Co) compositions. The shield layers may be fabricated from, for example, a soft magnetic material such as nickel-iron (Ni—Fe). Back bias magnet 30 may be fabricated from a permanent magnet material such as, for example, a cobalt-platinum (Co—Pt) alloy.
The operation of read head 10, according to one aspect of the invention is described in conjunction with
If spacer layer 126 is nonmagnetic and electrically conducting, it may be fabricated from, for example, copper. If spacer layer 126 is nonconducting, it may be fabricated from, for example, aluminum oxide (Al2O3 or AlxO where x may be not be an integer) or magnesium oxide. Ferromagnetic layers 122 and 124 may be fabricated from magnetic materials, such as, for example, nickel-iron-cobalt (Ni—Fe—Co) compositions. The shield layers may be fabricated from, for example, a soft magnetic material such as nickel-iron (Ni—Fe). Back bias magnet 130 may be fabricated from a permanent magnet material such as, for example, a cobalt-platinum (Co—Pt) alloy.
The operation of read head 110 according to one embodiment is described in conjunction with
The operation of read head 110 is similar to that discussed for read head 10 and schematically illustrated in
The formation of reader 10 with trapezoidal back bias magnet 30 shown in
The formation of reader 110 with trapezoidal back bias magnet 130 and trapezoidal reader stack 120 shown in
While the present disclosure has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the technology. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the provided technology not be limited to the particular embodiment(s) disclosed, but will include all embodiments falling within the scope of the appended claims.
Claims
1. A magnetic sensor comprising a trilayer stack disposed between an air bearing surface (ABS) and a back biasing magnet, the back biasing magnet and trilayer stack each shaped substantially as trapezoids along a plane extending from a first side shield to a second side shield and perpendicular from the ABS to provide a predetermined micromagnetic magnetization shape in the trilayer stack.
2. The magnetic sensor of claim 1, wherein the back bias magnet has a magnet width, as measured parallel to the ABS, that reduces as it approaches the ABS.
3. The magnetic sensor of claim 2, wherein the trilayer stack has a stack width, as measure parallel to the ABS, that reduces as it approaches the ABS.
4. The magnetic sensor of claim 1, wherein the trilayer stack has a pair of stack sidewalls extending from the ABS at a first predetermined angle and the back biasing magnet has a pair of magnet sidewalls extending away from the ABS at a second predetermined angle, the first and second angles being the same.
5. The magnetic sensor of claim 1, wherein the trilayer stack has a pair of stack sidewalls extending from the ABS at a first predetermined angle and the back biasing magnet has a pair of magnet sidewalls extending away from the ABS at a second predetermined angle, the first and second angles being different.
6. The magnetic sensor of claim 1, wherein the biasing magnet provides vertical bias to the trilayer stack.
7. The magnetic sensor of claim 1, wherein the biasing magnet comprises a hard magnetic material.
8. The magnetic sensor of claim 7, wherein the hard magnetic material is a cobalt-platinum based alloy or iron-platinum based alloy.
9. The magnetic sensor of claim 1, wherein the back biasing magnet is physically separated from the trilayer stack by an insulating layer.
10. The magnetic sensor of claim 1, wherein the back biasing magnet has a front surface facing a rear surface of the trilayer stack, the rear surface configured to have a greater width, as measured parallel the ABS, than the front surface.
11. The magnetic sensor of claim 1, wherein the back biasing magnet has a front surface facing a rear surface of the trilayer stack, the rear surface configured to have an equal width, as measured parallel the ABS, as the front surface.
12. An apparatus comprising:
- a trilayer stack disposed between an air bearing surface (ABS) and a back biasing magnet, the back biasing magnetic magnet and trilayer stack shaped substantially as trapezoids to provide a predetermined C-type micromagnetic magnetization shape in at least one ferromagnetic free layer of the trilayer stack.
13. The apparatus of claim 12, wherein the trilayer stack is disposed between lateral side shields on the ABS.
14. The apparatus of claim 13, wherein the lateral side shields are physically and magnetically isolated from the trilayer stack and back biasing magnet by an insulating layer.
15. The apparatus of claim 13, wherein each lateral side shield has a shield sidewall facing both the trilayer stack and back biasing magnet, the shield sidewall continuously angled from the ABS to match an angle of at least one sidewall of the trilayer stack and back biasing magnet.
16. The apparatus of claim 12, wherein the back biasing magnet provides bias to the trilayer stack in a direction generally perpendicular to the ABS.
17. A magnetic element comprising a trilayer stack disposed between an air bearing surface (ABS) and a back biasing magnet, the back biasing magnet and trilayer stack shaped substantially as trapezoids to provide a predetermined C-type micromagnetic magnetization shape in at least one ferromagnetic free layer of the trilayer stack that resists switching to a predetermined S-type micromagnetic magnetization shape.
18. The magnetic element of claim 17, wherein the predetermined C-type micromagnetic magnetization shape is retained in response to a state of a negative or positive bit.
19. The magnetic element of claim 17, wherein the predetermined C-type micromagnetic magnetization shape is present in each ferromagnetic free layer of the trilayer stack.
20. The magnetic element of claim 19, wherein the predetermined C-type micromagnetic magnetization shape of a first ferromagnetic free layer vectors in an opposite direction from the predetermined C-type micromagnetic magnetization shape of a second ferromagnetic free layer.
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Type: Grant
Filed: Jan 17, 2013
Date of Patent: May 13, 2014
Patent Publication Number: 20130128390
Assignee: Seagate Technology LLC (Scotts Valley, CA)
Inventors: Jiaoming Qiu (Saint Paul, MN), Kaizhong Gao (Shoreview, MN), Yonghua Chen (Edina, MN), Beverley Craig (Culmore), Zhongyan Wang (San Ramon, CA), Vladyslav A. Vas'ko (San Jose, CA)
Primary Examiner: Brian Miller
Application Number: 13/743,607
International Classification: G11B 5/33 (20060101); G11B 5/127 (20060101);